In recent years improvements in computer and semiconductor technology have enabled the prices of relatively sophisticated personal computers to be reduced to the point that they may be used in a wide variety of applications. As a consequence, personal computers have become enormously popular.
Much of the popularity of these personal computers results from the ability of magnetic disk drives to provide permanent storage for large amounts of data at a reasonable cost. To accommodate conflicting demands, a personal computer typically includes both a floppy disk drive and a hard disk drive. A floppy disk drive is advantageous in that it is less expensive and the disks that store the data can be easily removed and reinserted so that data stored on hundreds of different disks can be made available to the computer. However, the data transfer rate between a floppy disk and the computer is relatively slow, each floppy disk can only hold 1.2 MByte or less data and the manual loading of and unloading of floppy disks is relatively inconvenient and time consuming.
In contrast, hard disks tend to be more expensive, but they typically hold 30 MBytes or more of data and the data transfer rate between the disk drive and the computer control processing unit random access memory is much faster than with a floppy disk so that a data processing task can proceed much more quickly. Although it is known to provide removable hard disks, the extreme sensitivity of hard disks to dust particles and damage has precluded such removable disks from becoming popular in personal computers. The typical hard disk associated with a personal computer thus has a nonremovable disk media that is sealed within a dust free environment.
The present invention relates to a hard disk controller system which can accommodate either fixed hard disks or removable disks. The removable hard disks are removed as a sealed unit so as to avoid problems of dust contamination and damage to the media. A hard disk may thus be removed and substituted by another hard disk or used on another computer much like a floppy disk. At the same time the advantages of high data transfer rate and large storage capacity are maintained.
The hard disk control system of the present invention provides data buffering to further increase data transfer rates, high speed continuous noninterleaved access, disk storage locations that may be write-protected or even fully masked from application programs or even the operating system. Techniques are provided to assure proper insertion of a disk drive and to verify that a proper disk drive model has been inserted. A computer user may thus transport a complete software environment including operating system, programs and data to any computer having a compatible receptacle in a small box having the size of a full height 5 1/4 inch disk drive or less.